Question 1

During most of systole,left ventricular pressure exceeds aortic pressure,allowing blood ejection.

Accepted Answer

During systole, the left ventricle contracts and increases pressure, which eventually pushes open the aortic valve, and allows the blood to eject into the aorta. During this process, the left ventricular pressure is higher than aortic pressure which helps in blood ejection. Therefore, the statement is true.

Question 2

An electrocardiogram would be useful for diagnosing diseases involving the valves of the heart.

Accepted Answer

An electrocardiogram (ECG) is a test to measure the electrical activity of your heart. It can help detect abnormal heart rhythms, but it does not provide direct information about the heart valves. Other tests such as echocardiography or cardiac catheterization are needed to diagnose heart valve diseases.

Question 3

The sinoatrial node is normally the heart's pacemaker because it has the fastest spontaneous rate of depolarization.

Accepted Answer

The sinoatrial node is located in the right atrium of the heart and sets the pace for the rest of the heart's electrical activity. It has the fastest spontaneous depolarization rate, which allows it to regulate the heartbeat.

Question 4

The left ventricle has to pump more blood than the right ventricle because the left ventricle has to pump blood through the whole body,not just the pulmonary system.

Accepted Answer

The left ventricle does not pump more blood than the right ventricle; both ventricles pump the same volume of blood. However, the left ventricle pumps blood at a higher pressure to overcome the greater resistance of the systemic circulation compared to the pulmonary circulation.

Question 5

A major difference between the contractile cardiac cells and the cells in the cardiac conducting system is that the contractile cells do not undergo spontaneous depolarization.

Accepted Answer

Contractile cardiac cells require an external stimulus to depolarize, whereas cells in the cardiac conducting system, like pacemaker cells, can spontaneously depolarize.

Question 6

The inherent pacemaker discharge rate of the sinoatrial node is 72 beats per minute.

Accepted Answer

The inherent pacemaker discharge rate of the sinoatrial node is variable and can range from 60-100 beats per minute.

Question 7

At rest,more blood flows per minute to the skin and abdominal organs than to the lungs.

Accepted Answer

The answer of At rest,more blood flows per minute to...

Question 8

The QRS wave of the ECG corresponds to depolarization of the atria.

Accepted Answer

The QRS wave of the ECG corresponds to depolarization of the ventricles, not the atria.

Question 9

The wave of contraction that spreads through the ventricles starts at their tips and flows upward.

Accepted Answer

The contraction of the ventricles, known as ventricular systole, begins at the apex (tip) of the heart and moves upward towards the atria, facilitating efficient blood ejection into the arteries.

Question 10

The only time during the cardiac cycle that the AV valves are open is systole.

Accepted Answer

The AV valves are open during diastole to allow blood to flow from the atria into the ventricles. They close during systole to prevent backflow of blood.

Question 11

In general the parasympathetic nervous system's effects on the heart are to reduce activity through its release of acetycholine and binding with muscarinic receptors,but there is no significant effect observed on the ventricular cardiac muscle,compared to other parts of the heart.

Accepted Answer

The parasympathetic nervous system primarily affects the sinoatrial node and atrioventricular node, reducing heart rate and conduction velocity, but it has minimal direct effect on ventricular muscle contractility.

Question 12

The determinant for whether blood ejection occurs during ventricular contraction or whether filling occurs during ventricular relaxation is the pressure difference across the heart valves.

Accepted Answer

The pressure difference across the heart valves determines whether blood ejection or filling occurs during ventricular contraction or relaxation, respectively. This is because blood flow is driven by pressure gradients, and the heart valves ensure that blood flows in the proper direction.

Question 13

Cardiac muscle cannot undergo tetanus because its absolute refractory period lasts almost as long as the muscle twitch.

Accepted Answer

Cardiac muscle has a longer refractory period compared to skeletal muscle, which prevents tetanus from occurring. The refractory period is the time during which the muscle cannot contract again, and in cardiac muscle, it lasts almost as long as the twitch duration. This ensures that the heart can fill with blood before it contracts again, preventing complications such as arrhythmias.

Question 14

Normal heart sounds are produced by the slamming shut of the AV valves at the end of diastole and the aortic and pulmonary valves at the end of systole.

Accepted Answer

This statement is true. Normal heart sounds are produced by the closing of the heart valves, specifically the AV valves (tricuspid and mitral valves) at the end of diastole (when the heart is relaxed and filling with blood) and the aortic and pulmonary valves at the end of systole (when the heart is contracting and pumping blood out). These sounds can be heard with a stethoscope and are known as the "lub-dub" sound of the heartbeat.

Question 15

During stimulation of the parasympathetic nerves,plasma levels of epinephrine increase.

Accepted Answer

During stimulation of the parasympathetic nerves, plasma levels of epinephrine do not increase. This is because the parasympathetic nervous system is responsible for the "rest and digest" response and does not release epinephrine (also called adrenaline), which is a hormone released by the sympathetic nervous system in the "fight or flight" response.

Question 16

The myocardial cells receive their blood supply from the cardiac arteries that branch off from the aorta.

Accepted Answer

The answer of The myocardial cells receive their blood supply...

Question 17

An ectopic focus is an area of the myocardial conducting system,other than the atrioventricular node,that initiates cardiac depolarization.

Accepted Answer

The answer of An ectopic focus is an area of...

Question 18

Sympathetic stimulation of cardiac muscle produces stronger and faster contractions because the concentrations of calcium in the sarcoplasm are reduced by the activity of actively transporting proteins pumping it out of the cell.

Accepted Answer

Sympathetic stimulation of cardiac muscle actually results in an increase in calcium concentration in the sarcoplasm, which leads to stronger and faster contractions. This is due to the activation of calcium channels and increased release of calcium from the sarcoplasmic reticulum.

Question 19

Long-term studies show that the risk for heart attack and stroke doubles for every 20 mm increase in diastolic pressure and 10 mm Hg in systolic pressure.

Accepted Answer

This statement is true, as multiple long-term studies have observed this trend in blood pressure and cardiovascular risk.

Question 20

The left ventricle has a thicker wall than the right ventricle because the left ventricle has to pump blood against a higher pressure.

Accepted Answer

The left ventricle pumps oxygenated blood to the body, which requires a higher pressure than the right ventricle's job of pumping blood to the lungs for oxygenation. As a result, the left ventricle has a thicker wall to pump blood against a higher pressure.

Quiz 12: Cardiovascular Physiology